The loss of an eye by accident or disease is not an uncommon occurrence. Further, some individuals are born without an iris, with a defective iris, or without a globe. Because such loss or defect impacts facial appearance, it is most desirable to either compensate for it, mask it, or provide some artificial means to replace it. One approach is to simply employ a patch to cover the eye and/or socket. However, a patch necessarily draws attention to the absence or inoperability of the eye. Accordingly, it does little to improve the physical appearance of the wearer, while often adding to the emotional stress incident to such loss or defect.
It has recently been known to replace a missing eye with a prosthesis often referred to as an "artificial" or "glass" eye. Prior to 1940, most ocular prostheses were constructed of ground glass. However, the shortage of such glass during World War II led to the creation of pyroplastic prostheses with thin glass overlays. These overlays had painted surfaces which resembled the human eye. Because the surface could only have one image, a person employing such a device would require a series of prostheses to simulate the pupillary size in exposure to varying degrees of light. In the absence of such multiple prostheses, the "artificial" nature of the prosthesis would become readily apparent when the pupil size of the prosthesis was different from that of the wearer's natural eye. Of course, as the wearer would pass through environments of various light intensities during the day, the pupil of the natural eye would necessarily dilate or contract, differing in appearance from that of the prostheses in the absence of the physical change in prostheses by the wearer.
In about 1960, a method for placing two or more images on a rotating cylinder within the prosthesis was developed. A magnetic wand was used to locate the desired image in the center of the pupullary field. While representing a significant improvement, the system was limited in that its size and weight was prohibitive, and the change in pupil size was necessarily mechanically attained.
U.S. Pat. No. 4,332,039 teaches a magnetic type of prosthesis of the type just discussed. U.S. Pat. No. 3,480,971 teaches a mechanical dilator which is responsive to muscle movement within the eye socket to achieve the desired control over pupil size. U.S. Pat. No. 4,272,910 teaches the utilization of a photosensor and liquid crystal plate to attain the appearance of dilation in an artificial eye, with such dilation being responsive to light stimulation.
U.S. Pat. No. 4,601,545, 2,760,483, 2,721,316, 4,551,149, 4,436,376, and British Patent 2,016,276 are viewed as being of general interest to the concept of ocular prosthesis of the type presented herein.
The prior art has recognized the need to simulate dilation and contraction of the pupil in an ocular prosthesis, but the devices presented to achieve such a feature have typically been complex, expensive, and given to problems incident to failure and maintenance. Additionally, the prior art structures have typically been heavy and cumbersome, often uncomfortable when received in the socket of the wearer. Typically, the prior art structures have either been mechanical magnetic, electronic, or electromechanical, all requiring periodic maintenance, repair of replacement.
The art is devoid of an active pupillary prosthesis which is absent moving parts or electronis control. It is further absent such a prostheis employing photochromic materials capable of simulating dilation and constriction without electrical or mechanical action, but by simple chemical reaction to incident light. Specifically, the art is devoid of such an active pupillary prosthesis in which the scleral shell to be received by an implant is integrally provided with such photochromic materials. The art is further devoid of an applique which may be adhered to an existing scleral shell to provide such an active pupillary feature. The art is further devoid of a contact lens employing photochronic materials for the appearance of an active pupillary response which may be received by a defective eye for cosmetic masking.